High Glucose Treatment Limits Drosha Protein Expression and Alters AngiomiR Maturation in Microvascular Primary Endothelial Cells via an Mdm2-dependent Mechanism

Diabetes promotes an angiostatic phenotype in the microvascular endothelium of skeletal muscle and skin. Angiogenesis-related microRNAs (angiomiRs) regulate angiogenesis through the translational repression of pro- and anti-angiogenic genes. The maturation of micro-RNA (miRs), including angiomiRs, requires the action of DROSHA and DICER proteins. While hyperglycemia modifies the expression of angiomiRs, it is unknown whether high glucose conditions alter the maturation process of angiomiRs in dermal and skeletal muscle microvascular endothelial cells (MECs). Compared to 5 mM of glucose, high glucose condition (30 mM, 6-24 h) decreased DROSHA protein expression, without changing DROSHA mRNA, DICER mRNA, or DICER protein in primary dermal MECs. Despite DROSHA decreasing, high glucose enhanced the maturation and expression of one angiomiR, miR-15a, and downregulated an miR-15a target: Vascular Endothelial Growth Factor-A (VEGF-A). The high glucose condition increased Murine Double Minute-2 (MDM2) expression and MDM2-binding to DROSHA. Inhibition of MDM2 prevented the effects evoked by high glucose on DROSHA protein and miR-15a maturation in dermal MECs. In db/db mice, blood glucose was negatively correlated with the expression of skeletal muscle DROSHA protein, and high glucose decreased DROSHA protein in skeletal muscle MECs. Altogether, our results suggest that high glucose reduces DROSHA protein and enhances the maturation of the angiostatic miR-15a through a mechanism that requires MDM2 activity.

Alphastatin-C a new inhibitor of endothelial cell activation is a pro-arteriogenic agent in vivo and retards B16-F10 melanoma growth in a preclinical model

Most characterized angiogenic modulators are proteolytic fragments of structural plasma and/or matrix components. Herein, we have identified a novel anti-angiogenic peptide generated by the in vitro hydrolysis of the C-terminal moiety of the fibrinogen alpha chain, produced by the snake venom metalloprotease bothropasin (SVMP), a hemorrhagic proteinase in Bothrops jararaca venom. The 14-amino acids peptide (alphastatin-C) is a potent antagonist of basic fibroblast growth factor, induced endothelial cell (HUVEC-CS) proliferation, migration and capillary tube formation in matrigel. It also inhibits cell adhesion to fibronectin. The basis of the antagonism between bFGF and alphastatin-C is elucidated by the inhibition of various bFGF induced signaling pathways and their molecular components modification, whenever the combination of the stimuli is provided, in comparison to the treatment with bFGF only. To corroborate to the potential therapeutic use of alphastatin-C, we have chosen to perform in vivo assays in two distinct angiogenic settings. In chick model, alphastatin-C inhibits chorioallantoic membrane angiogenesis. In mouse, it efficiently reduces tumor number and volume in a melanoma model, due to the impairment of tumor neovascularization in treated mice. In contrast, we show that the alphastatin-C peptide induces arteriogenesis, increasing pial collateral density in neonate mice. alphastatin-C is an efficient new antiangiogenic FGF-associated agent in vitro, it is an inhibitor of embryonic and tumor vascularization in vivo while, it is an arteriogenic agent. The results also suggest that SVMPs can be used as in vitro biochemical tools to process plasma and/or matrix macromolecular components unraveling new angiostatic peptides.

Cytokine Analysis: A Fresh Perspective

It is recognized that a balance of different cytokines (synergistic versus antagonistic cytokines) determines the outcome in regulation of different actions such as inflammation, polarization, and secretion of macrophages, induction and secretion of T helper cells, and angiogenesis. It is also known that cytokine secretion is highly variable between individuals. These facts red flag the practice of only comparing absolute values of 1 or 2 cytokines in various studies. It is recognized that ratios of opposing functions yield better quantification of the equilibrium than just observing single values. It is the purpose of this article to (1) emphasize the need to measure a combination of cytokines selected in a manner so that ratios of these may be derived to yield more information about the homeostasis in body and (2) to offer a list of synergistic and antagonistic cytokines from which future investigators may select for more meaningful results.

Semaphorins in Angiogenesis and Autoimmune Diseases: Therapeutic Targets?

The axonal guidance molecules, semaphorins, have been described to function both physiologically and pathologically outside of the nervous system. In this review, we focus on the vertebrate semaphorins found in classes 3 through 7 and their roles in vascular development and autoimmune diseases. Recent studies indicate that while some of these vertebrate semaphorins promote angiogenesis, others have an angiostatic function. Since some semaphorins are also expressed by different immune cells and are known to modulate immune responses, they have been implicated in autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus and systemic sclerosis. We conclude this review by addressing strategies targeting semaphorins as potential therapeutic agents for angiogenesis and autoimmune diseases.

Role of angiogenesis and vascular remodeling in chronic obstructive pulmonary disease

Recently, angiogenesis and pulmonary vascular remodeling in COPD has been investigated. It has been hypothesized that endothelial dysfunction might be an initiating event that promotes vessel remodeling in COPD. Inflammatory tissue--a pivotal pathological feature of COPD--often hypoxic, can induce angiogenesis through upregulation of factors such as VEGF or FGF and regulators of angiogenesis such as chemokines (CXC family), acting either as angiogenic or angiostatic. Angiopoietins are distinct molecules that act in association with VEGF at different stages of angiogenic process. The regulation of angiogenesis is determined by a dual, yet opposing balance of angiogenic and angiostatic factors that promote or inhibit neovascularization, respectively, not yet elucidated in detail in COPD. Recent studies suggested an increased expression of VEGF in pulmonary muscular arteries of patients with moderate COPD and also in smokers with normal lung function. This was also associated with enlargement of the arterial wall. However, in patients with severe emphysema, the expression of VEGF tended to be low, despite intense vascular remodelling. Furthermore, it has been suggested that VEGF might be involved in the pathogenesis of emphysema through apoptotic mechanisms. Experimental studies showed that the lung microvascular endothelial cells (including the alveolar septal capillary cells) are particularly vulnerable and dependent on VEGF for their survival. Apoptosis of endothelial, leading to the loss of capillaries may well be a central mechanism in patients with emphysema and muscle wasting. This review article summarizes the current knowledge regarding the contribution of vascular remodeling, as well as the pathogenetic and therapeutic implications of pivotal angiogenic mediators, in COPD.